The disruptive effects of elevated lead levels on the functioning of developing hypothalamic pituitary-adrenal axis (HPAA) has not been well examined. The purpose of this research investigation is to examine the effect of lead exposure on the ontogeny of HPAA. In this investigation, Sprague-Dawley rats will be administered lead at postnatal day (PND) 1 until PND 21, Blood levels of lead in neonatally exposed animals and their control will be monitored. A animals will be assessed and evaluated at PND 21, 35 and 120 for the adrenal function using different experimental paradigms. In one experiment we will examine the effect of lead exposure on the function of the hypothalamus, pituitary and the adrenal gland. In another experiment we will evaluate the adrenocortical function of lead- treated animals by evaluating basal levels of corticosterones, ACTH, glucocorticoid receptors, hypothalamic biogenic amines, plasma glucose levels and liver glycogen. We will also examine the effect of acute and chronic stress on the hormonal profile of these animals. In a final experiment we will evaluate the toxic effect of lead on the maturation of the adrenal cortex. The outcome of this research should help in the understanding of how neonatal exposure to lead can modify the adrenal cortical function.